Reputation is where it's at -- that's what I tell clients. After all, the vast majority of ISP spam filtering engines are fueled by data relating to your sending reputation -- complaints, bounces, and engagement. But even with that, people still often ask about content, which isn't necessarily my area of expertise. So, instead of telling you whether or not it's safe to use the word "free" in a subject line (it is), allow me to link you to this smart article by IBM's Len Shneyder: 5 Design Tips That Will Lower Your Spam Scores.
